Electromagnetic-based acoustic energy harvester

The development of an electromagnetic-based acoustic energy harvester using Helmholtz resonator is reported in this paper. The working principle, fabrication and characterization of the harvester are discussed. The developed harvester comprises of an orifice, cavity, flexible membrane, moving magnets and a fixed wound coil. The harvester is characterized under acoustic energy at different sound pressure levels (SPL´s) and is subjected to both forward frequency sweep (FFS) and reverse frequency sweep (RFS). At resonance and under 125 dB SPL, the harvester produced a maximum open circuit rms voltage of 667 mV. However, when connected to an optimum load of 52 ohm, it generated an rms load voltage of 319.8 mV. At resonance and when subjected to 125 dB SPL the maximum power of 1966.77 μW is delivered to the load, that leads to a maximum power density of 133.6 μW/cm³ for the developed harvester.